Brake drum



Feb. 11, 1930. v. BENDIX 41,746,925

BRAKE DRUM Original Filed May 2. 1928 `Patented YFeb. .11, 1.930

. UNITED- STATES PATENT OFFICE.D

VINCENT BENDIX, OF SOUTH BEND, INDIANA, ASSIGNOR T BENDIX BRAKE COMPANY ,i i n OF SOUTH BEND, INDIANA, A CORPORATION OF ILLINOIS :BRAKE DRUM GriginalA application led May 2, 1928, Serial No. 274,677. Divided and this application filed February 28,

f 1929. Serial No. 343,319;

This invention relates toimprovements in brake drums and is a division of my applican tion Serial No. 274,677, filed May 2, 1928,

patented July 16, 1929 No. 1,7 20,815. 'l

In the past brake drums have been made of relatively easily corrodible material such as iron. As this ferruginous base metal corrodes, not only does itbecome unsightly, but

it also becomes seriously weakened by reason of the fact that the iron of relatively high h eats. This corrosion is practically cumulative; the iron oxide which is formed not only c does not provide al protective coating but ac-y 'fcelerates subsequent corrosion or oxidation tensile strength is replaced by a deposit of iron oxide which possesses substantially no strength. This corrosion or oxidation is ac` are of lowcorrodibility and of the desirable V high ltensile strength. Y

Another object is to provide a brake drum of lhigh strength, low corrodibility and hardness. Y

posite brake structure of a ferruginous-material and another metal.

A further object is to provide a brake drum Y of a ferruginouslbase metal with which is combined certain othermetals which increase the strength and lower the corrosion.

The single figure on the'drawing is an enlarged and diagrammatic villustration of a brake drumproducedaccording to Fthe inf 40 vention. i

`Aspointed out in'my parent application, the availability, ease of manufacture and machining, and the relative cheapness of deepdraw steel'recommends its use in brake drum` structures. Ordinary steel, however, is relatively easily corroded. When used in-brake drums it is subjected to constant wettings and corrosion sets in. This, as is known, consists in oxidation of the iron and, as has been 5 pointed out, is accelerated by the frictional Another object is to provide a novel comof the `underlying body. i This disadvantage may in a measure be cured by manufacturing a drum from chromium, vanadium, zirconium or other alloy steels. These materials not only are characterized by extremely low corredibility but are also of a high tensile strength. While these materials do present major advantages, they are considerably more expensive than the ordinary steel employed.

According to the purpose of this invention, a brake drum maybe produced which presentsall of the advantages of the alloy steels, and in addition provides certain added ad? van-tages.

In ,the application referred to there was described and claimed a brake drum which comprised a ferruginous' ufoundation metal on the exterior' of which was deposited aplating of chromium. The advantage of a thin coat of chromium or similar relatively non-V oXidizable metals maybe combined with the highly protective features of a thick coating of such metal. The present preferred'methodof accomplishing these will serve to indicate the underlying principles of the invention. 30 These advantages may be achieved by t veating a brake drum, or the material from w ich a brake drum is made, with metallic zinc'so 'as to form a coating of zinc over the outer or l 'exposed surface of the drum. It will be un- 85 Aderstood, of course, that if desired the interior surface of the drum may similarly be i treated or the treatment localized to any Vde-` sired area.

As shown in the drawing, the zinc^may be '00 cemented to the iron by galvanizing or sherardizing in the well known manner.

In the electro-chemical-series zinc is given as electro-positive to iron. This is tanta mountto saying that it has a greater -solu- I6 tion pressure or tendency to dissolve. Therefore, when Yit is in contact with moisture, the zinc becomes the dissolving electrode and the iron .the electrode on which the deposits are formed. As aresult, the zinc notonly me 100 chanically protects the iron, that is to say forms a protective coating thereover, but it also provides electro-chemical protection.

The sherardizing ormetallic `cementation may be carried out according to any accepted practice. These methods in general consist in cleaning the` metal to be treated and then f packing it in zinc dust within an air-tight metal container. The container is then heated and tumbled. Asa general rule blue dust or a mixturelof blue dust? and zinc oxide are employed. These processes are generally carried out atf temperatures ranging from 350 to 375 C., the temperature employed being dependent upon the desired zinc content of the alloy and the composition of the Zinc dust.A For the present use itis preferable that the treatment be continued for a sufcient period of time so as to insure a substantial quantity of l zinc in the outer coat- 1 ing after diffusion has taken place.

The resulting structurev then comprises a metallic member made up of iron and a zinc iron alloy, the outer surface of the member having a larger percentage of zinc. During continued use, particularly at high temperatures, the zinc tends to diffuse throughthe iron and decreases the concentration of zinc in the outer layer. Since the zinc iron alloy, like the zinc, is anodic to iron, it is necessary only to carry out the process sufficiently long to insure a zinc content which willadequately protect the iron. C

After the ferruginous material has been treated with zinc so as to form a coating or skinof a zinc compound, the surface may then be plated with, the desired metal of low corrodibility, in the present instance with.

' chromium. This may be carried'out by the electrodeposition method, explained in the copending application above referred to.

As the result of the provision of an intermediate layer of zinc, the deposited skin or film of chromium maybe very thin and hence no great care need be exercised to avoid perforatlons. If such -perforations do occur i they will have no deleterious effect since, as

has been pointed out, the zinc provides electro-chemical protection for the iron. If the moisturehas access to the zinc coating, thisy will slightly tarnish, but its unsightliness is in no way comparable to that of iron oxide'.

The metal Zinc has been described as merely indicative, of a number ofspecific metals which may be used. As has been explained, the protective feature of zinc dependsA in part on its electro-chemical-characteristics;

thus in place of zinc the iron may be coated with any suitable substance which is electropositive to it and upon which may be formed an adherent coat of the plating metal. Similarly .in lieu of chromium, one may employ other metals such as nickel and cadmium,`

which are depositable as lustrous and nonoxidizing films.

vplurality-.,of layers. of metals of different corrosion characteristics. y

3L A brake drum of ferruginous-metal hav- -ing an outer coating of a lustrous and relatively non-corrodible metal, and 'an' interposed portion of a metal which provides electro-chemical protection for the ferruginous metal. y

4. A brake drum comprising a ferruginous foundation metal having an exterior surface of a metallic substance of low corrodibility and a second metallic substance interposed between the said surface and foundation metal which is anodic to thev ferruginous metal. i

5. A brake drum comprising a foundation`metal, an exterior surface comprising a metallicsubstance of lower ,corrodibility than v'the foundation metal and an intermediatel portion having embodied ltherein a metallic substance which is anodic to the foundation metal.;

6. A brake drumv comprising a foundation metal having an-exterior surface of chromium and an intermediate portion in which zinc is embodied.-

7. A brake drum comprising a'ferruginous foundation material, the interior frictional engaging surfacefof which is surfaced with chromium. p

8./ A brake drum comprising a ferruginous foundation metal having an interior frictional engaging surface-of lower corrodibility vthan the foundation metal.

9. A brake drum comprising a ferruginous foundation metal having an interior frictional engaging surface which contains chromium.

J 10. A brake drum comprisin a ,ferruginous foundation metal with whc two other metals of differential physical characteristics are associated. Y

11. A material adapted for use in the manufacture of brake drumscomprising a ,ferruginous foundation metal having a zinc containing portion and a chromium containing portion overlying the zinc containing layer.

12. A brake drum comprising a ferrugnous core, a zinc containing layer on each face of the core and a relatively/,non-oxidizable metal plated on the zinc containing layers.

13. A. brake drum comprisin a ferruginous foundation metal having ayers of 1ntegrally bonded non-ferrous metals.

14. A brake .drum comprising a ferruginous foundation metal having a. galvanized portion and a relatively non-oxidizable metal plated on said portion.

15. A brake drum comprising a ferruginous foundation metal having a. galvanized portion and a surface of chromium plated on said portion.

In testimony whereof I aiiix my signature.

VINCENT BENDE. 

